Pentafulvenes are a unique class of compounds that originally attracted attention due to their propensity to display nonbenzenoid aromaticity. Subsequently, they were recognized as valuable synthons for the construction of a wide range of compounds by virtue of their ability to display multiple cycloaddition profiles. Naturally, this area of organic chemistry has experienced rapid growth over the last five decades, fueled by elegant work showcasing the unique reactivity of pentafulvenes in a plethora of cycloaddition reactions. In this Review, we have attempted to provide a systematic account of the methods for the generation of pentafulvenes, their rich and varied cycloaddition chemistry, organometallic reactions, and theoretical studies that support their versatility. Further, we have highlighted their applications in the synthesis of a variety of complex structural frameworks. It is our conviction that this Review will be useful to a wide range of chemists, and will spur further research in this promising area.

No abstract

No abstract

Transition-metal-catalyzed carbonylation reaction using chloroform as CO surrogate to synthesize carbonylated heterocyclic moieties.

Copper-mediated carbon–heteroatom bond-forming reactions involving a wide range of substrates have been in the spotlight for many organic chemists. This review highlights developments between 2010 and 2019 in both stoichiometric and catalytic copper-mediated reactions, and also examples of nickel-mediated reactions, under modified Chan–Lam cross-coupling conditions using various nucleophiles; examples include chemo- and regioselective N-arylations or O-arylations. The utilization of various nucleophiles as coupling partners together with reaction optimization (including the choice of copper source, ligands, base, and other additives), limitations, scope, and mechanisms are examined; these have benefitted the development of efficient and milder methods. The synthesis of medicinally valuable or pharmaceutically important nitrogen heterocycles, including isotope-labeled compounds, is also included. Chan–Lam coupling reaction can now form twelve different C–element bonds, making it one of the most diverse and mild reactions known in organic chemistry.1 Introduction2 Construction of C–N and C–O Bonds2.1 C–N Bond Formation2.1.1 Original Discovery via Stoichiometric Copper-Mediated C–N Bond Formation2.1.2 Copper-Catalyzed C–N Bond Formation2.1.3 Coupling with Azides, Sulfoximines, and Sulfonediimines as Nitrogen­ Nucleophiles2.1.4 Coupling with N,N-Dialkylhydroxylamines2.1.5 Enolate Coupling with sp3-Carbon Nucleophiles2.1.6 Nickel-Catalyzed Chan–Lam Coupling2.1.7 Coupling with Amino Acids2.1.8 Coupling with Alkylboron Reagents2.1.9 Coupling with Electron-Deficient Heteroarylamines2.1.10 Selective C–N Bond Formation for the Synthesis of Heterocycle-Containing Compounds2.1.11 Using Sulfonato-imino Copper(II) Complexes2.2 C–O Bond Formation2.2.1 Coupling with (Hetero)arylboron Reagents2.2.2 Coupling with Alkyl- and Alkenylboron Reagents3 C–Element (Element = S, P, C, F, Cl, Br, I, Se, Te, At) Bond Forma tion under Modified Chan–Lam Conditions4 Conclusions

A novel palladium catalyzed protocol for the synthesis of cyclopentene fused heterocycles from diazabicyclic alkenes and ortho-functionalized aryliodides has been elaborated. The reaction can be tuned toward the formation of either 3,4-disubstituted cyclopentenes or cyclopentene fused heterocycles by careful manipulation of the reaction parameters. A number of cyclopentene fused benzofurans and indole derivatives were prepared in excellent yield by utilizing the developed methodology.

No abstract

An approach to expand the diversity of terpenes to novel polycyclic skeletons with contiguous stereogenic centers is described. An unprecedented 8-oxabicyclo[3.2.1]octane motif was obtained in quantitative yield by photoirradiation of zerumbone in the presence of a catalytic amount of Lewis acid. The vital role of light in the isomerization of double bonds in zerumbone, which ensued cyclization via tertiary carbocation intermediate, emulates a biosynthetic route. Synthetic diversification of the phototransformed product afforded epoxy derivatives with up to seven contiguous stereogenic centers and eight-member ring fused tricyclic motifs. The present work sheds light on the possible role of UV irradiation in the biosynthesis of oxo-bridged tricyclic structures from polyene terpenes.Letter pubs.acs.org/OrgLett